body {
  margin: 0;
}
.mt_20px {
  margin-top: 20px;
}
.mr_20px {
  margin-right: 20px;
}
.mb_20px {
  margin-bottom: 20px;
}
.ml_20px {
  margin-left: 20px;
}
.mx_20px {
  margin-left: 20px;
  margin-right: 20px;
}
.my_20px {
  margin-top: 20px;
  margin-bottom: 20px;
}
.m_20px {
  margin: 20px;
}
